Chelsio iSCSI Offload Driver (Initiator and Target)

Links: https://svnweb.freebsd.org/changeset/base/292740
Contact: Navdeep Parhar <navdeep@chelsio.com>

A new driver, cxgbei, that enables hardware accelerated iSCSI with Chelsio's T5
and T4 based offload-capable cards has been committed to HEAD.  Both Initiator
and Target are supported.  The wire traffic is standard iSCSI (SCSI over TCP as
per RFC 3720 etc.) so an Initiator/Target using this driver will interoperate
with all other standards compliant implementations.

Hardware assistance provided by the T5 and T4 ASICs includes:
a) Complete TCP processing.
b) iSCSI PDU identification and extraction from the byte oriented TCP stream.
c) Header and/or data digest generation and verification.
d) Zero copy support for both transmit and receive.

The cxgbei driver is sponsored by Chelsio Communications.

Outstanding items:
a) cxgbei(4) man page is missing but will be committed shortly.
b) The driver is in advanced stage QA and will see some bugfixes and performance
enhancements in the very near future.  MFC is possible as soon as the QA cycle
completes.